The broad objective of the proposed research is to obtain a basic understanding of endocrine changes during sexual maturation of the rhesus monkey. The specific objectives are a) to continue studies of circulating LH, FSH, testosterone, and 17 beta-estradiol from birth through early adulthood; b) to determine whether gonadotropin secretion is under hypothalamic control in the infant; c) to determine when negative feedback of gonadal steroids on LH and FSH secretion becomes established; d) to determine whether chronic androgen treatment results in precocious maturation of hypothalamo-hypophyseal-ovarian function. Experiments conducted thus far by the principal investigator indicate that circulating LH. determined by radioimmunoassy (0-0) for monkey LH, is extremely high in both sexes during infancy. These concentrations gradually decrease and by 6 months of age, are comparable to those of the adult. These increased levels of LH in the infant are not observed when another radioimmunoassay (HCG-Rh) for monkey LH is used. Because of the marked discrepancy between these two systems, the initial phase of the proposed research will be conducted to examine some of the biological, immunological, and physicochemical properties of the material detected by the 0-0 system, and to validate a radioimmunoassay(s) for measuremnt of biologically active LH (and "infant LH" if such a form exists) in the sexually immature monkey.